Carbon Nanobowls Filled with MoS2 Nanosheets as Electrode Materials for Supercapacitors

Simultaneously achieving high gravimetric capacitance and volumetric capacitance remains a major challenge in the development of supercapacitor electrode materials. A class of hollow carbon nanobowls (HCNBs) with a unique semiconcave geometry has been synthesized by a facile template method. The HCNBs can serve as a nanoreactor for the in situ space-confined growth of ultrasmall size, few layer two-dimensional (2D) molybdenum disulfide (MoS2) nanosheets. When used as the electrode materials for supercapacitors, the MoS2 nanosheets inside HCNBs named MoS2@HCNBs demonstrated outstanding gravimetric capacitance (560 F g–1 at 0.2 A g–1) and volumetric capacitance (874 F cm–3) at the same time. The cycling performance of MoS2@HCNBs (94.4% capacitance retention after 5000 cycles) is also much higher than HCNB@MoS2 in which the surfaces of HCNBs were covered by the 2D MoS2 nanosheets. Several factors have been leading to the boosted performance, and the mechanisms have been analyzed. The HCNBs with high surface area, developed porosity, and ultrathin carbon shells promote the rapid electrolyte penetration and provide a conductive pathway for excellent ion and electron transport. The ultrasmall few layer MoS2 nanosheets inside the HCNBs help to induce extra electrochemical double-layer capacitance as well as higher pseudocapacitance. More importantly, the semiconcave HCNBs can protect the structural stability of MoS2 nanosheets and contribute an enhanced packing density to further improve the volumetric capacitance of the hybrid MoS2@HCNBs.